Ironsand is a kind of titanomagnetite ore and has been maturely used through direct reduction (DR) and melting separation (MS) processes. As an intermediate parameter, pre-reduction degree (PRD) can be controlled in the upstream DR, and has a considerable influence on metal/slag separation in subsequent MS. Thus, the effects of PRD on the properties of melting separation slag from prereduced ironsand are studied in order to ensure the melting separation sufficient at the condition of slag with high titanium oxide content. The softening, melting, and flowing temperatures of slag show different variation trends along with PRD changing, and the slag at 90% PRD has the narrowest softening-flowing temperature interval. The viscosity of slag of 90% PRD also shows the proper smelting characteristic. Moreover, Raman spectra results indicate the increase PRD reduces the depolymerized product Si-O-M (metal), which is mainly caused by the decreasing of network-modifier FeO. Polymerization degree ψ ((Q 3 þ Q 2 )/(Q 1 þ Q 0 )) illustrates the high PRD is consistent with the complicated silicon network structures, especially when PRD is larger than 90%. Figure 2. The original profile of slag samples and melting samples with the height accounting for 75, 50, and 25% of the original sample height during the heating process, a-e) represent the slags at the PRD of 70, 90, 95, 97, and 100%, respectively. www.advancedsciencenews.com www.steel-research.de steel research int.